Metso Paper Inc.

Valmet Corporation

Juha Wahlroos

Pentti S Lehtonen

Kari Niemi

Juhani Vestola

Harri Kuosa

Bjarne Hellman

Jussi Tuomela

Jorma Majava

A press roll such as the center roll of a press or the back-up roll of an extended-nip press roll, used in a pulp, paper, board or finishing machine, has a coating with an intermediate sealed layer. The corrosion resistance and impermeability of the roll coating, particularly of such a coating that is made by thermal spraying, can be improved by way of sealing. The coating comprises a porous outermost surface layer made out of a ceramic or ceramic-metal material applied by thermal spraying and at least one sealed layer situated between the outermost surface layer and the roll mantle.

Method for sealing of a coating on a roll

A roll for use in the manufacture of paper and board, a press roll, in particular a center roll in a press, a backup roll for an extended-nip press roll, a hot press roll, or equivalent, which is in direct contact with a wet paper web, or a calender roll, a method for manufacturing the same and a coating composition therefor including an adhesion layer arranged on the frame part of the roll and a ceramic layer arranged on the adhesion layer. The ceramic layer has a thickness of from about 100 &mgr;m to about 2000 &mgr;m and includes from about 50% to about 95% by weight of Cr O and from about 3% to about 50% by weight of TiO , or from about 50% to about 80% by weight of Al O and from about 20% to about 50% by weight of ZrO , or exclusively Al TiO . The outer face of the ceramic layer is finished until the roughness Ra is from about 0.2 &mgr;m to about 2.0 &mgr;m and/or the porosity of the outer face of the roll is from about 1% to about 20%. In addition to or instead of TiO , the ceramic layer may contain oxides of aluminum, silicon, zirconium, magnesium, manganese, tin, tungsten and mixtures thereof.

Method for manufacturing a paper or board machine and coating composition therefor

A press roll for a paper or board machine, a method for manufacturing a roll for a paper or board machine and a coating composition for a roll which enable the roll to endure difficult corrosion conditions. An adhesion/corrosion-protection layer having a thickness of from about 150 &mgr;m to about 300 &mgr;m is applied onto the frame part of the roll by a high-velocity flame spraying technique. The adhesion/corrosion-protection layer contains a nickel-chromium alloy. A tight-ceramic layer having a thickness from about 50 &mgr;m to about 150 &mgr;m is applied onto the adhesion/corrosion-protection layer by a high-velocity flame spraying technique and includes from about 50% to about 100% of Al,O,and optionally includes up to about 50% of TiO,and/or any amount of Al,TiO,. A porous ceramic layer is applied onto the tight ceramic layer. The tight-ceramic layer may include only Al,TiO,instead of Al,O,, with or without TiO,.

Press roll with a ceramic coating, method for manufacturing the same and coating composition

A press roll for a paper or board machine, a method for manufacturing a roll for a paper or board machine and a coating composition for a roll which enable the roll to endure difficult corrosion conditions. An adhesion/corrosion-protection layer having a thickness of from about 150 .mu.m to about 300 .mu.m is applied onto the frame part of the roll by a high-velocity flame spraying technique. The adhesion/corrosion-protection layer contains a nickel-chromium alloy. A tight-ceramic layer having a thickness from about 50 .mu.m to about 150 .mu.m is applied onto the adhesion/corrosion-protection layer by a high-velocity flame spraying technique and includes from about 50% to about 100% of Al.sub.2 O.sub.3 and optionally includes up to about 50% of TiO.sub.2 and/or any amount of Al.sub.2 TiO.sub.5. A porous ceramic layer is applied onto the tight ceramic layer. The tight-ceramic layer may include only Al.sub.2 TiO.sub.5 instead of Al.sub.2 O.sub.3, with or without TiO.sub.2.

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Polokka, Finland

Juha Wahlroos